Carbon black manufacture



Aug. 13, 1963 J. L. MASON, JR 3,100,589

CARBON BLACK MANUFACTURE Filed Aug. 21, 1958 5 Sheets-Sheet 1 FIG. I

\ MI: A vf \NVE'.NTOR

JAMES L. MASON, JR.

Aug- 13, 1963 J. L. MASON, JR 3,100,689

CARBON BLACK MANUFACTURE Filed Aug. 21, 1958 3 Sheets-Sheet 2 INVENTOR.JAMES L. MASON, JR.

Aug.,13, 1963 J. L. MASON, JR

CARBON BLACK MANUFACTURE s sheets-sheet s Filed Aug. 2l, 1958 mmPmDJO ZwmJNNOZ hmmm ....O mmEDZ OOM lNvENToP:A JAMES L. MASON, JR.

ma me-44M L )a n ATTZRQS United States Patent O This invention relatesto the manufacture of carbon black and, more particularly, toimprovements in processes therefor of the type in which a hydrocarbonoil, or similar liquid carbon-containing compound, is subjected topartial combustion in a relatively quiescent zone withl a restrictedamount of oxygen, whereby a portion of the oil is burned and theremainder is decomposed to carbon black by the heat thus generated.

A process of this type has been described and claimed in United StatesPatent 2,779,665, in accordance with which a gently-owing, relativelyuniform current of air is passed upwardly through the lower end of anunobstiuoted, vertically-elongated, heat-insulated furnace chamber and agas-atomized spray of liquid hydrocarbon, of high molecular weight andhigh aromaticity, initiated in the lower end of the chamber, is injectedupwardly into the chamber, at a relatively high velocity, in contactwith the air, whereby a portion of the hydrocarbon is burned in thelower end Vof the chamber and there is established in the furnacechamber above the zone of combustion a lazy, substantially non-oxidizingor reducing upwardly rising atmosphere of hot furnace gases at atemperature above the decomposition temperature of the remaininghydrocarbons. p

In that operation, the hydrocarbon is sprayed upwardly through theupwardly rising air and hot furnace gases at an initial velocitysuilicient to carry the spray high into the chamber but insufficient tocause `it to impinge on the upper wall thereof. The air is introducedinto the lower end of the furnace chamber in an amount much smaller thanthat required to burn all of the hydrocarbon and at a rate, and in amanner, such as to establish a uniform, non-turbulent upwardly driftingcurrent through the chamber at a velocity within the range of 1 foot tosiX feet per second. Under these conditions, there is formed within thechamber a smoke blanket which fills the entire upper portion of thechamber extending downl' wardly for a distance approximating one-half tothreefourths of the height of the chamber.

The process just described has been found especially advantageous inproducing so-called high structure blacks, having high oil absorptioncharacteristics, from highly aromatic oils, for instance creosote oils,cracked petroleum residues, coal tars, coal tar oils and the like. Thepresent invention, in one of its aspects, constitutes an improvement inthe process of said Patent 2,779,665, but its utility is not restrictedto the specific operating conditions, or to the charging stock, thereindescribed.

The oil absorption characteristics of a carbon black have beenrecognized to vary with the aggregate surface area of the black. As themean particle diameter of the carbon black particles decreases, itssurface area, frequently expressed as square meters per gram, generallyincreases. However, the oil absorption of carbon blacks is also known tobe influenced by a characteristic of the black known as st1ucture, whichis a joining together of the carbon particles to form reticulate chains.For a carbon black of a given mean particle diameter, a high oilabsorption characteristic is an indication of such structure.

High structure is a desirable property of carbon black for somepurposes. For instance, blacks having high structure improve theextruding properties of rubber ICC compositions compounded with suchblacks. For other purposes, a low or moderate oil absorption orstructure is more desirable.

A known way of controlling oil absorption, within limits, is by theselection of the feed stock to be decomposed for producing the carbonblack. It is known that the use of paraffinic type feed stocks normallytends totproduce carbon blacks of low oil absorption for a given meanIparticle diameter. On the other hand, the use of aromatic oils generallytends to produce carbon blacks of relatively higher structure and highoil absorption. However, the oil absorption characteristic of a carbonblack is normally very difficult to control independently of surfacearea and charging stock.

Usually infurnace operation, conditions, such as air ratios and thelike, are so set as to produce a carbon black of the required iineness,the oil absorption being independently controllable only within arelatively narrow range.

A disadvantage of using parainic oils for producing carbon blacks of lowoil absorption is that the yield of carbon black per gallon of oil isrelatively low. The aromatic feed stocks inherently produce higheryields, but also higher structure.

The present invention provides method and means whereby the oilabsorption characteristics of a carbon black may be controlled andvaried over a wide range, independently of the feed stock used andindependently of the particle size range of the resultant black.

The invention also provides means whereby the productionrate of a givenfurnace may be greatly increased by increasing the charging rate withoutmaterial change in the quality of the carbon black produced.

The invention will now be described and illustrated with reference t0the following drawings of which:

FIG. 1 is a vertical sectional view of a carbon black furnace embodyingmeans especially adapted to the carrying out of my improved process,

FIG. 2 is a transverse horizontal section along the line 2-Z of FIG. 1,

FIG. 3 is an enlarged somewhat fragmentary view, partly in section, ofan assembly used in accordance with my invention for injecting thehydrocarbon oil into the furnace chamber, and

FIG. 4 is a graphic illustration of the increase in production rate of agiven furnace made possible by my present invention.

The `furnace of FIG. 1 comprises a vertical elongated chamber 1 tofcylindrical cross-section surrounded by circular wall 2, taperinginwardly at its upper end, and constructed of suitable furnacerefractory and heat-insulating materials, as is well-'known to the art.The lower end of the furnace chamber is provided with a partition 3 offurnace refractory, beneath which there is an lair chamber 4. Amultiplicity of symmetrically positioned airducts 5 extend throughpartition 3 through which air passes from the air chamber into chamber 1for supporting the partial combustion of the oil.

Combustion air is passed to the air chamber under moderate pressure fromany convenient source through conduit 6 which ente-rs tangentially intothe annular air duct 7 and passes therefrom into the air chamber 4through the downwardly directed, symmetrically positioned perforations8.

The rate at which airis introduced `through duct 6 [is so regulated lasto obtain the desired quantity of air passing upwardly through chamber 1at the desired velocity, usually within the range of l foot to 6 `feetper second, and more advantageously within the range of 1 foot to 3 feetper second, calculated for a temperature of 2400o F.

The oil to be partially burned and partially decomposed to carbon blackis introduced into -the furnace chamber 3,1oo,ese

by means of the spray assembly represented at 9 and more clearly shownin FIG. 3 of the drawing and, with reference to which, the assembly willhereinafter be more fully described. n The resultant gaseous suspensionof carbon black passes from the upper end of the chamber Ithrough iiue1G into duct 1.1 leading to conventional carbonblack separating andcollecting apparatus, not necessar] here to describe.

An essential feature of the present invention is the manner in which theoil is introduced into the furnace chamber, since it is by variation inthis feature of the invention that the oil absorption orstructure'characteristic of the resultant carbon black is independentlycontrolled.

I have found most surprisingly that the oil absorption characteristic ofa carbon so produced can be controlled at will and varied over asubstantial range, independently of the type of charging'stock used 'andof the mean particle :diameter of the carbon black particle, byinjecting the oil into the furnace chamber as a cluster of parallel,gas-atomized liquid sprays and varying the number of sprays of thecluster.

A spray assembly comprising a cluster of such sprays, which has beenused with particular advantage in carrying out the present invent-ion,is illustrated by FIG. 3. The assembly shown comprises a cluster of 8closely spaced, symmetrically arranged spray nozzles 9` so positionedthattheir respective axes are parallel. It will be understood that thenumber of spray nozzles in the cluster may be varied considerablydepending upon the desired results. It appears to be essential, however,that the spaces between the nozzles be closed against the upward ow ofair. AIn the apparatus shown, the body of the assembly meets thatrequirement.

The respective spray nozzles shown comprise an outer hollow cap 11internally threaded into sleeve I2 at 13. Sleeve 12 is in turn threadedonto the upper end of nipple 14 at 15 and the lower end of the nipple isthreaded at 16 into the cover plate i7 of the oil chamber 18 whichconstitu-tes the upper end of the housing 19 and which is separated bypartition 20 from steam chamber 21 in the lower end of housing 19. Thesespray nozzles fare spaced apart a distance of 1% inches-2 inches betweencenters.

The nozzle also comprises `'an inner element composed of a tube 22threaded into partition 20 'at its lower end and lopening into steamchamber l21. The passageway through this tube is constricted at itsupper end to form an orifice -23 leading into the chamber within thehollow cap 11. The upper end of tube 22 is surrounded by helical guides24.

In operation, oil under pressure is forced from the oil chamber upwardlythrough the annular duct su-rrounding tube Z2 and along the flights ofthe helical guides 25 into the cap 11. Steam under pressure passes fromsteam chamber 21 through tube 22 and is jetted ythrough orifice 23,forcefully impinging on, land atomizing, the oil land the resultantmixture is sprayed into the furnace chamber through orifices 25extending through cap `11.

It will be understood that the invention is not restricted to theparticular construction of the spray nozzle shown bu-t that othernozzles adapted to the gas atomization of liquid oils may be used. Mostadvantageous results have been obtained using spray nozzles having anangle of spread of about 30i degrees.

In the assembly shown, steam under pressure is fed to chamber 21 throughsteam conduit 26 which extends coaxi-aily through tube 27 forming anannular passageway 28 through which the oil, preferably preheated, ischarged under pressure to chamber 18.

Due .to the high temperature of the furnace chamber, usually of theorder of 2300 F. `or higher, there is danger of coke-forming pyrolysisof the oil being passed to the spray nozzles. I kavoid this difficultyby thermally insulating `the incoming oil'frcm the high temperatures ofthe furnace chamber.

In the assembly shown in FIG. 3, I provide an annular dead-air space 29positioned coaxially with respect to the con-duit 28 and which, in turn,is surrounded by an annular passageway Sti formed by coaxiallypositioned cylindrical walls Si and 312 and'end wall 33. Water or othercooling medium is discharged into the inner end of conduit 3@ throughpipe 34, iiows outwardly along tube 31 and is discharged through outlettube 3S. The dead-air space 29 is vented through end wall E53` at 36 andtube 27 is held in position by lugs 37. Except as previously noted, thevarious elements of the assembly may be fastened together in anysuitable manner, for instance by welding las indicated at 3S.

In practice, I have found it advantageous to fill the spaces between thespray nozzles with a plastic refractory material as protection from thehigh furnace temperatures.

As noted above, the oil absorption characteristics of the carbon blackmay be controlled :and regulated, in accordance with the presentinvention, gby varying the nurnber of spray nozzles of the cluster.While I am unable presently to account for this phenomena, I have foundthat, for a given ltype of charging stock, the oil absorptioncharacteristic of the resultant carbon black can be materially decreasedby increasing the number of spray nozzles of the cluster and,conversely, the oil absorption characteristic can be materiallyincreased by decreasing the number of spray nozzles of the cluster.

Where 1 to 3 spray nozzles are used, `as described in the above-notedPatent No. 2,779,665, a carbon black of maximum structure, or oilabsorption, for the particular feed stock, is obtained. But as thenumber of spray nozzles is increased, other conditions remainingconstant, the structure of the resultant carbon black has been found todecrease. Similarly, as the number of spray nozzles is increased, theoil load, i.e. charging rate to the furnace, may be increased withoutmaterial change in the qual-ity of the resultant black. I have, withadvantage, used clusters of as many as 18 sprays. Clusters of even morethan 18 sprays may be used but such large clusters tend to occupy toogreat a proportion of the cross-sectional area of the furnace chamberand operation becomes more idiiiicult to control.

This variation in oil absorption and structure can be effected, by mypresent method, regardless of the particular type of feed stock used,`as fwill be illustrated by the following speciiic examples.

EXAMPLE I This operation was carried out in apparatus substantially asshown in the drawings except that the number of spray nozzles in the`spray assembly used in the respective runs was varied as indicated. Thediameter of the furnace chamber was 8.5 feet, I D. The feed stock usedin each of these runs was creosote oil, land in each run the spreadangle lTof the respective spray nozzles was about 30. The number ofsprays and other yoperating conditions used in each run land thecharacteristics of the resultant carbon black lare set forth in thefollowing tabulation:

Table I Run No 1 2 3 p.s.l Calculated steam, volume at 300 F., .hInitial spray nozzle velocity, ft./sec. (cale). Au' velocity, {11./sec.(calc.) Color rating, ABC

Oil absorption, gallons per lbs.-- Yield, lbs. per gallon Since ABCcolor value is an indication of mean particle diameter, it will appearthat each of the carbon blacks produced was of the same fineness and, inspite of that fact and the fact that the same feed stock was used ineach run, the oil absorption characteristics of the black droppedsharply with an increase in the number of sprays.

EXAMPLE I1 In each of `the following runs, the feed stock used was a No.6 fuel oil of relatively low arcmaticity. The apparatus was the salme asthat used in ythe preceding runs, except that the furnace diameter was6\.5,feet, LD. The number of sprays and operating conditions and thecharacteristics of the resultant carbon black are set forth in the.following tabulation:

Table 1I Run No 1 2 3 4 Number oi sprays.. 3 4 5 8 Air volume, M c..h 3232 32 32 Oil, g.p.h 180 180 180 180 Atcmizing steam, p.s. 40 40 40 40Calculated steam volume at 290 F., cih- 2, 520 3, 360 4, 220 6,720Initial Vspray nozzle velocity, it./sec.

(calc.) 686 686 686 636 Air velocity, It./Sec. (oalc.) 1. 43 1. 43 1.43 1. 43 Color rating, ABC 54 55 55 Oil absorption, gallons per 100 lbs14. 5 12. G 10. 4 8.0 Yield, lbs. per gallon 2. 2 2` 4 2. 6 2. 5

Here also the iineness of the resultant carbon blacks of the respectiveruns ywas practically the same, as indicated by ABC color, and thechanging stock was identical. Neveritheless, there was a sharp decreasein oil absorption value with the increase in the number of sprays used.

EXAMPLE III In yfurther .series of runs using No. 6` fuel oil as 'thecharging stock in the furnace lof the preceding example and underconditions set Vforth'in the following tabulation,

It has heretofore been found particularly diiiicult t0 varyindependently the oil absorption characteristics of a carbon blackproduced .from parafiinic type oils such as No. 6 ifuel oil. The presentinvention provides means whereby this can be readily accomplished. Also,as shown by the yield increase in Tables II and III, the presentinvention provides means whereby the yield of carbon black per `gallonof :oil used may frequently be materially increased, without decrease inmean particle diameter, by increasing :the number of sprays used.

The air velocities 4given in `the foregoing tabulations were calculatedfor a temperature of 2400 F. The initial spray nozzle velocities `andsteam volumes are approximate values calculated with-out taking intoaccount expansion due to temperature increase on leaving the nozzle, theorifice discharge coeiiicient or the oil volume.

The relationship of permissible oil load to the number of sprays in theclusters used, lfor increasing production rate without change inquali-ty, is illustrated by the graph constituting FIG. 4 of thedrawings in which the production rate in pounds of carbon black per houris plotted against the number of sprays. In leach of these runs, thefeed stock was No. 6 fuel oil, hereinafter more fully described, and theratio of air to foil was maintained at .33 1, as in the precedingExample Ill.

The furnace used in these runs was that used in EX- a-mples II land III.In each instance, the ABC color value ci 4the resultant black was 50-51and the oil absorption val-ue was 12J-12.4 `gallons of oil per 100pounds of the black. The increase in production rate was, of course, dueto an increase in chargingfrate, which would normally result in `amarked change in the quality of the black produced. However, byincreasing the number of sprays, in accordance with my presentinvention, it was possible materially to increase the charging ratewhile maintaining the quality of the black substantially constant.possible, in accord-ance with m-y present invention, by varying thenumber of sprays used, independently to control the structurecharacteristics of the black |at -a given production rate or tomaterially increase production rate while holding the structure of theblack constant.

rThe characteristics of the respective oils used in the foregoing runsare set iorth in 'the following tabulation:

Table IV Creosote No. 6 fuel oil oil It will Ibe understood that theinvention is not restricted to the speciiic types of foil illustratedybut is applicable generally to normally liquid hydrocarbons landsimilar carbon-containing compounds, referred to collectively in theappended claims as hydrocarbon oil.

In addition .to use in rubber compounding, the carbon blacks produced inaccordance lwith my present invention are well `adapted for other uses.`For instance, the black so produced having the higher oil absorptioncharacteristics are particularly useiul in the manufacture of dry cellbatteries, :and the lower oil absorption blacks are particularly usefulin `the manufacture 'of electrical resistors, electrodes 'and the like.In rubber compounding, the blacks of higher oil `absorption lareespecially adapted for use with synthetic rubber, while the lower oilabsorption carbon blacks are more desirable `for use in the compoundingof natural rubber.

Without intending to be 'bound to iany theory las to why thesesurprising results are obtained, I advance the following as a possibleexplanation. Where :a single spray is used, the upwardly rising air isin Contact with the entire periphery of that spray tand imay readily bedrawn into the interior :ot the spray by eduction. Where two or threesprays are used, a very substantial proportion of the periphery ofythose lsprays is also in contact with the rising air. However, wherethe number yof sprays is increased beyond three, there is developedwithin the interior of the cluster a zone in which there is a relativelyhigh concentration of the hydrocarbon droplets. In conjunction withthis, by reason of the Afact that the zone is shielded on all sides fromthe upwardly rising lair current by the surrounding sprays, and the factthat no air is permitted to rise between the spray nozzles, and the:fact that there is only a low degree 'of turbulence of the rising airby which it might be diffused into this zone, this zone of relativelyhigh hydrocarbon concentration is also relatively free from oxygen.

As thc number of spray nozzle-s is increased, the horizontal area ofthis zone will also be increased and the shielding of this zone from thesurrounding air current will become even more eiective. It is my presentbelief that the surprising decrease in oil absorption is, in some way,related to the lestablishing of this interior zone of high hydrocarbon,and low oxygen, concentration.

I claim:

1. In the process ttor producing furnace caribou blacks by the partialcombustion of hydrocarbon oils whereby a Thus it isY oil is injectedupwardly into 'the chamber as la high velocity gas-atomized sprayinitiated in the .-l-ower end of the chamber, whereby a portion of thehydrocarbon is burned in the lower portion of the chamber and there isestablished inthe furnace chamber above said zone of combustion a lazy,substantially non-oxidizing, upwardly rising atmosphere of hot lfurnacegases at a tempenature above the :decomposition temperature of theremaining hydrocarbons, the improvement which comprises injecting theoil into the fur-nace chamber as 4a cluster of closely spaced,gas-atomized spray streams having substantially parallel Y axes ofsymmetry arranged labout -a central Zone substantially coaxially withthe vertical axis of the furnace charnber, the number `of the spraystreams in the cluster being i-n excess of three, the spnay streamsbeing suliiciently close to form a protective barrier to the entrance oflair later- `al-ly into said central zone, and shielding said centralzone against passage of air upwardly thereinto.

2. The process of claim 1in which the upward velocity f the air currentthrough the furnace chamber is within the range of 1 foot to 6 feet persecond.

3. The process of claim 2 in which the upward Velocity of the aircurrent through the chamber is within the range of 1 foot to 3 feet persecond.

4. The process of claim l in which the hydrocarbon vused is a highmolecular weight, highly aromatic residual oil.

5. The process of claim l in which the hydrocarbon used is a fuel oilrelatively high in paraffinic constituents. 6. In the process 'forproducing furnace carbon blacks by the partial combustion of hydrocarbonoils whereby a Vgently-ilowing, relatively uniform current of air ispassed upwardly through the lower portion of an unobstructed,vertically-elongated furnace chamber and the hydrocarbon oil is injectedupwardly into the chamber as a high velocity gas-atomized sprayinitiated in the lower end of the chamber, whereby a portion of thehydrocarbon is burned in the lower portion of the chamber and there isestablished in the chamber above said zone of combustion a lazy,substantially non-oxidizing, upwardly rising atmosphere of hot furnacegases at a temperature above Athe decomposition temperature of theremaining hydrocarbons, the method of controlling the oil absorptionchar acteristic of the resultant black which comprises injecting the oilinto the furnace chamber as a cluster of closely spaced, gas-atomizedspray streams" having substantially parallel axes of symmetry arrangedabout a central zone substantially coaxially with the vertical axisofthe furnace chamber, the number of the spray streams in the clusterbeing in excess of three, the number of spray streams depending upon thedesired low value in the oil absorption characteristic of the resultantblack, the greater the number of oil streams, the lower the oilabsorption characteristic, the spray streams being Sulliciently close toform a protective barrier to the entrance of kair laterally into saidcentral zone, and shielding said central zone against passage of airupwardly thereinto.

7. In the process for producing furnace carbon blacks by the partialcombustion of hydrocarbon oils whereby a gently-flowing,y relativelyuniform current of air is passed upwardly through the lower portion ofan unobstructed, vertically-elongated furnace chamber and thehydrocarbon oil is injected upwardly into the chamber as a high velocitygas-atomized spray initiated in the lower end of the chamber, whereby aportion of the hydrocarbon is burned in the lower portion of the chamberand there is established in the chamber above said zone of combustion alazy, substantially non-oxidizing, upwardly .rising atmosphere of hotfurnace gases at a temperature above the decomposition temperature ofthe remaining hydrocarbons, the method of increasing the production rateper unit volume of charging stock of a given furnace by increasing thehydrocarbon oil charging rate, without substantial change in thequality-of the resultant carbon black, which comprises injecting the oilinto the furnace chamber as a cluster of closely spaced, gasatomizedspray streams having substantially parallel axes of symmetry arrangedabout a central Zone substantially coaxially with the vertical axis ofthe furnace chamber, the number of the spray streams in the clusterbeing in excess of three, the number of spray streams depending upon thedesired charging rate, the greater the number vof spray streams thehigher the charging rate, the spray streams being sufficiently close toIform a protective barrier to the entrance of air laterally into saidcentral zone, and shielding said central zone against passage of airupwardly thereinto.

References Cited in the le of this patent UNITED STATES PATENTS2,779,665 Heller Ian. 29, 1957

1. IN THE PROCESS FOR PRODUCING FURNACE CARBON BLACK BY THE PARTIALCOMBUSTION OF HYDROCARBON OILS WHEREBY A GENTLY-FLOWING, RELATIVELYUNIFORM CURRENT OF AIR IS PASSED UPWARDLY THROUGH THE LOWER PORTION OFAN UNOBSTRUCTED VERTICALLY-ELONGATED FURNACE CHAMBER AND THE HYDROCARBONOIL IS INJECTED UPWARDLY INTO THE CHAMBER AS A HIGH VELOCITYGAS-ATOMIXED SPRAY INTITATED IN THE LOWER END OF THE CHAMBER, WHEREBY APORTION OF THE HYDROCARBON IS BURNED IN THE LOWER PORTION OF THE CHAMBERAND THERE IS ESTABLISHED IN THE FURNACE CHAMBER ABOVE SAID ZONE OFCOMBUSTION A LAZY, SUBSTANTIALLY NON-OXIDIZING, UPWARDLY RISINGATMOSPHERE OF HOT FURNACE GASES AT A TEMPERATURE ABOVE THEDECOMPOSTITION TEMPERATURE OF THE REMAINING HYDROCARBONS, THEIMPROVEMENT WHICH COMPRISES INJECTING THE OIL INTO THE FURNACE CHAMBERAS A CLUSTER OF CLOSELY SPACED,